Process for the purification of gases for the synthesis of ammonia



June 27, ETlENNE ET A PROCESS FOR THE PURIFICATION OF GASES FOR THESYNTHESIS OF AMMONIA Patented June 27, 1933 Ai'JFRED-ETIENNE AND ALBERTGOSSELIN, or MoN'rERnAiI; Annnoennnu CHAFFAUT,"

OF .VARENNES. SUE SHINE, FRANCE,

I ANONYME POUR LET'UDE .85 LEXPLOITATION' DES rams, FRANCE ASSIGNQRS "r0LAIR mourns, SOCIETE pnoonss son THE runIrIcA'rIoN or eAsEs ron THESYNTHESIS OF AMMONIA Application filed me s, 1930, Serial No, 461,022;and in France July 9, 1929. i

The present invention relates to the purification of gases for the'sy'nthesis of ammonia, which has for its object the elimination of smallquantities of carbonic acid which may be, contained in the gas feedingan installa tion for the synthesis of ammonia.

It has been. found out, particularly when this synthesis is' attainedbycausing the gases to circulatein aclosed circuit, that is to say whenthere is added to the fresh gas feeding the installation the gaseshaving passed over the catalyzer, and not combined, a solid deposit isformed at the point where the mixture of the twoigas'es takes place,originating from the combination of the traces of carbonic acid of thefresh gas, with the small quantities of ammonia contained intheicirculation gas. This deposit, which takes place, even when thefresh gas contains carbonic acid in too weak a proportion to bedetrimental to the syntl1esis,obstructs at length the piping and rendersdifiicult a continuous working. a I i A known means for remedying thisdisadvantage consists in the preliminary puri ,fying of the fresh gas toa sufficient high degree, for example by' washingv with the aid ofliquid ammonia or by action ofmetals or of alkaline amidesin the solidstate or melted .or inthe state-of dissolution. I These processes,however, are onerous and out of I proportion with the smallness'of thequanti- "ties of carbonic acid which it is desired to eliminate. 1 I

The present inventioirhas for its, object to make this disadvantagedisappear in a simple and practically costless manner. It

consists in letting into, the gas which feeds the installation forthesynthesis of the am :1 40 monia, a'quantity of steam suffi'cing for thewater formed during the further condensation of this steam to-carry awayin the dissolved lstate the whole of the ammonium carbonate at'themoment of its formation by 'reaction of-the carbonic acid, upon theamm'onia and the steam contained in the gas.

" 1 A practical means for carrying out this process consistsinfinjecting' into the compressed and still warm gas issuingfrom thecompressor or from the purificationtube eliminating the carbon-monoxidebefore catalysis, a proportion of ammonia in the gaseous state largelycorresponding to the. quantity of carbonic acid-ito be eliminated, thento provoke, by cooling to a temperature PROCEIDES GEORGES CLAUDEL OFnear to the ambient temperature,'the condensation of the water; theammonium car- 7 bonate which forms remains dissolved and is easilyevacuated outside" the circuit at the and as applied to this lattercase.

In {this drawing, A represents the purifica- 7 tion tube for theffreshgases transforming the carbon-monoxide into methane by acatalyticreaction; however, in this transformation ofthe carbonm'onoxide, avery small quantity of carbonic acid is nearly always formedas accessory reaction of the purification reaction, according to theequation:

I This latter gas, repelled by G and'contain- 'ing a little ammonia,ismixed at Hwith the purified fresh gas coming out of theseparator C. Bythe derivation tube J furnished with a regulating cock X, a small partof the re'-, circulation gas is deducted'which is added at -Y to thegas, still hot, coming out offthe purification tube A and before thisgas is cooled in the refrigerant B. This fresh gas thus added withammonia passesinto the refrigerant B and, under the influence ofthetemperature, the carbonate of ammonia l forms, but it is immediatelydissolved by the gas thus freed of its carbonic acid no longer incursthe risk of provoking stoppages at the pointH' where it mixes with theprincipal part ofthe re-circulation gas.

Instead of sending the containing ammonia into Y, it could also be sentinto Z, as indicated in dotted line.

What we claim is 1. A process for the elimination of the carbon dioxidecontained in compressed fresh gases feeding a plant for the synthesis ofammonia, which comprises adding to the fresh gases a quantity of ammoniaat least equal" to-that which is necessary for fixing as ammoniumcarbonate the carbon. dioxide contained in the fresh gases, and aquantity of hyd'rogen'monoxide sufficient to allow the formation, at asufficiently low temperature,

of an aqueous solutionof the ammonium carbonate formed from the carbondioxide, the added ammonia, and a part of the hydrogen monoxide, andremoving said aqueous solu tion at said sufficiently low temperature.

2: A process forthe elimination of the carbon dioxide contained incompressed fresh gases feeding a plant for the synthesis of ammonia,which comprises adding to" the fresh gases'a quantity of ammonia at'least equal to that which is necessary for fixing as ammonium carbonatethe carbon dioxide contained in the fresh gases, said addition takingplace in the presence of a quantity ofhydrogen monoxide sufficient toallow the formation, at a sufficiently low temperature, of an'aqueoussolution of the ammonium carbonate formed from the carbon dioxide, theadded ammonia, and a part ofthe hydrogen monoxide, and removing saidaqueous solution at said sufficiently low temperature.

3. A process forthe eliminationzof the carbon dioxide contained in freshcompressed .gases feeding a plant for the synthesis of ammonia, whichcomprises adding to the Warm fresh gases water vapor and a quantity ofammonia at least equal to that which is necessary for-fixing as ammoniumcarbonatethe carbon dioxide of' the fresh gases, cooling said gases downto such a temperature as to cause the condensation of an aqueoussolution, and

removing saidaqueous solution, the temperature of the warmfresh gasesbeing sufficientlyhigh as to permit of the introduction therein of? aquantity of water vapor sufficient for forming, when thesubsequentcooling to a sufficiently low temperature takes place, an

aqueous'solution of the ammonium carbonate formed from the carbondioxide, the added ammonia, and a part of the water vapor introducedinto the fresh gases.

4. A process for the elimination of the carremoving said aqueoussolution, the temperature of the warm dampfrlesh gases beingsufficiently high as to permit of their con taining a quantity ofwater'vapor'suflicient for forming,when the subsequent cooling to asufficiently low temperature takes place, an 89 aqueous solution of'th'eammonium: carbonate formed from the carbondioxide, the added ammonia,and a part of the water' vapor' of the fresh gases.

5. A process fortheelimination of'thezcar. 3

bon dioxide contained in fresh compressed gases feedingapl'ant for thesynthesis ofammonia, which comprises adding-to: the fresh gases aquantity of ammonia at'least equal to that which is'necessaryforfixingas am- 90 monium carbonate the carbon: dioxide-of the fresh gases,saidf-resh gases containi'ngliquid Water in a quantity sufficientt'oiallow theformation of an aqueous solution of the am moniunrcarbonate formed, from the canbon 9 5 dioxide, the added ammonia, and a.part'of said liquid water, and removing'saidc aqueous solution; 1

64A- process as in claim'l 1n WhlCh ammonia isadd'ed inthe form of" apart of t'the T gases from the'ammonia synthesis which' have beenfreedtfrom the larger; part: ofthe ammonia contained therein.

' 7. A process fortheeliminatiomof'tlie. carbon dioxide contained infresh, compressed, ibs

carbon monoxide containing gases 1 feeding a plant" for" the synthesisof ammonia, which comprises catalytically combining the'scarlionmonoxide and apart ofthe-hydrogen of the fresh gases to methane,waterand eventually-' no traces of' carbon dioxide, adding ammoniaatothe fresh'gases,ucooling; the fresh gases down to such a temperatureascto cause the condensation of an aqueous solutlon, and re moving thesaid: aqueous solution the added lm ammonia being taken in aquantity'atileast equal to that which is necessaryforfixing as ammonium carbonatethe carbon: dioxide of the fresh gases and that eventually generatedsimultaneously with the methaneand water. v

8. A process for the elimination of the carbon dioxide contained infresh,.compressed, carbon monoxide containing; gases feeding a plant forthe synthesis of ammonia, whioh gases down to suchatemperatureiasito-cause the condensation of water, adding to the wateri carbon dioxide contained in fresh, comcontaining fresh gases aquantity of ammonia at least equal to that which is necessary for fixingas ammonium carbonate the carbon dioxide of the fresh gases and thateventually generated simultaneously with the methane and Water, andremoving the formed aqueous solution of ammonium carbonate.

9. A process for the elimination of the carbon dioxide contained infresh, compressed, carbon monoxide containing gases feeding a plant forthe synthesis of ammonia, which comprises catalytically'combining thecarbon monoxide and a part of the hydrogen of the fresh gases tomethane, water and eventually traces of carbon dioxide, adding to thefresh gases a portion of the gases from the ammonia synthesis whichhave, been freed from the larger part of the ammonia contained therein,coo-lingthe fresh gases down to such a temperature as to cause the,condensation of an aqueous solution, and removing said aqueous solution,the portion of the added gases from the ammonia synthesis being at leastthat which contains a quantity of ammonia sufiicient for fixing asammonium-carbonate the carbon dioxide of the fresh gases and thateventually generated simultaneously with methane and Water, and thetemperature of the'fresh gases being sufficiently high asto permit oftheir containing a quantity of water vapor suflicient for forming, whenthe subsequent cooling takes place, an aqueous solution of the ammoniumcarbonate formed 7 from the carbon dioxide, the added ammonia, and apart of the water;

10. Aprocess for the elimination of the pressed, carbon'monoxidecontaining gases feeding a plant for the synthesis of ammonia, whichcomprises catalyti'cally combining the carbon monoxide with a part ofthe hydrogen of the fresh gases to methane, water. and

the residual gases from the synthesis of am-' monia which have beenfreed from the larger part of their ammonia, and removing the aqueoussolution formed, the portion of the of ammonia sufficient for fixing asammonium carbonate the carbon dioxide of the fresh gases and thateventually generated simultaneously with methane and water, and thetemperature of the fresh gases being sufii ciently high as to permit oftheir containing a quantity of water vapor sufficient for forming, whenthe subsequent cooling takes place,

an aqueous solution of the ammonium carbonate formed from the carbond1ox1de, the

added ammonia, and a part of the water.

In testimony whereof, we afiix our signatures. I q

" ALFRED ETIENNE.

' ALBERT GOSSELIN.

ROGER DU CHAFFAUT.

.80 added gases from the ammonia synthesis I being'at least thatwhichcontains a quantity.

